microbit temperature sensor

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Unlock the World Around You: Measuring Temperature with the BBC micro:bit Sensor

Ever wondered how hot your lunchbox gets by recess, or how chilly it really is outside your window? The unassuming BBC micro:bit, a powerhouse of educational computing, holds the answer right on its circuit board. Its built-in microbit temperature sensor isn’t just a technical spec; it’s a gateway for students, hobbyists, and educators to bridge the digital and physical worlds. Forget complex setups – this accessible sensor empowers anyone to start gathering real-world temperature data instantly. Imagine a classroom buzzing as students monitor microbit temperature sensor readings to investigate insulation materials, or a citizen scientist tracking micro-climates in their garden. The possibilities ignite curiosity straight out of the box.

What Exactly is the micro:bit Temperature Sensor?

Contrary to what some might assume, the microbit temperature sensor isn’t a separate, dedicated component you plug in. It’s cleverly integrated onto the main processor chip itself. Technically, it measures the temperature of the silicon die of the Nordic Semiconductor nRF51822 system-on-chip (SoC) that acts as the micro:bit’s brain. This means its readings inherently reflect the temperature inside the micro:bit’s electronics, not the ambient air temperature directly surrounding it.

This distinction is crucial. While it provides valuable data, interpreting the microbit temperature sensor output requires understanding its context. Its readings are primarily influenced by the heat generated by the processor during operation. So, if you’re running intensive code, the sensor will report a higher temperature than when the micro:bit is idle. This characteristic makes it perfect for experiments involving the device’s own operation or as a relative indicator, but less ideal for pinpointing exact room or outdoor air temperature without careful calibration.

How the Magic Happens: From Silicon to Screen

The microbit temperature sensor utilizes a fundamental electronic principle. It’s based on a thermistor – a component whose electrical resistance changes predictably with temperature. Specifically, the micro:bit employs a Negative Temperature Coefficient (NTC) thermistor integrated into the chip. As the temperature rises, the resistance of this NTC thermistor decreases.

The micro:bit’s processor doesn’t measure resistance directly. Instead, it uses its built-in Analog-to-Digital Converter (ADC). Here’s the simplified sequence:

1. Voltage Reference: The processor applies a known reference voltage.
2. Voltage Divider: The thermistor (sensor) is part of a voltage divider circuit. Its changing resistance alters the voltage measured at a specific point in this circuit.
3. ADC Conversion: The ADC reads this varying voltage level and converts it into a digital number.
4. Software Interpretation: The micro:bit’s firmware (or your code) uses a calibration formula to convert this raw digital ADC value into a meaningful temperature reading in degrees Celsius (°C).

Putting it to Work: Coding the Temperature Sensor

The beauty of the micro:bit lies in its simplicity. Accessing the microbit temperature sensor is incredibly straightforward across its programming environments. Here’s how you do it in the most popular ones:

• MakeCode Blocks:

• Navigate to the Input category.

• Find the bright orange temperature (°C) block. This block returns the current temperature reading as a number.

• Use this block anywhere you need the temperature value – display it on the LED matrix, plot it on a graph, send it over radio, or store it for later analysis. Try a simple program like: forever loop -> show number block -> plug in temperature (°C). This continuously displays the temperature.

• MicroPython:

• Import the necessary module: from microbit import *

• Use the temperature() function. It returns the temperature in degrees Celsius as an integer.

• Example: current_temp = temperature() stores the reading in the variable current_temp. You can then display.scroll(str(current_temp)) to show it.

Calibration is Key: Getting More Accurate Readings

Since the microbit temperature sensor primarily measures the chip’s internal temperature, how can we use it to gauge the surrounding environment?

1. Allow Stabilization: Run your temperature reading code in a forever loop, but include a generous pause (e.g., 1-2 minutes) between readings. This gives the micro:bit time to cool down or warm up towards the ambient temperature after processing the code itself.
2. Subtract the “Processor Heat”: Run a very simple, low-power program that just reads the temperature and sleeps. Note the reading. Then run your actual, more complex program and read the temperature. The difference between these readings represents the heat added by running your main program. You can potentially subtract this offset from readings taken during active operation.
3. Relative Measurements Matter: Often, the change in temperature is more important than the absolute value. The microbit temperature sensor is excellent for tracking trends over time or comparing conditions (e.g., inside vs. outside a container, before vs. after adding insulation). Projects focusing on thermal conductivity, insulation effectiveness, or chemical reaction heat output are ideal applications.

Inspiring Projects: Beyond Just a Number

The true power of the microbit temperature sensor shines in creative applications:

• Microclimate Monitor: Place micro:bits in different locations (sunny spot vs. shade, indoor vs. outdoor, high vs. low shelf). Compare the microbit temperature sensor data over hours or days to map microclimates. Chart the data using MakeCode’s console or export it.
• Thermal Insulation Tester: Build small chambers using different insulating materials (foam, cardboard, wool, aluminum foil). Place an ice cube or a slightly warmed object inside each chamber along with a micro:bit. Use the microbit temperature sensor to track how quickly the temperature changes, revealing which insulator is most effective. This is a fantastic hands-on physics experiment.
• “Safe Zone” Alarm: Program the micro:bit to sound an alarm (use the speaker) or flash brightly if the temperature reading goes above or below a set threshold. Great for monitoring sensitive plants, pets, or even preventing electronics overheating.
• Data Logging Explorer: Combine the sensor with the micro:bit’s data logging capability (using its internal storage or an external SD card adapter). Record temperatures at regular intervals during a field trip, overnight, or during a science fair experiment. Analyze the data later to uncover patterns.
• Wireless Weather Network: Use the micro:bit’s radio feature! Multiple micro:bits with microbit temperature sensor readings can transmit their data to a central “base station” micro:bit, building a simple classroom or home wireless temperature monitoring network.

Important Considerations and Limitations

• Range and Accuracy: The microbit temperature sensor is designed for typical environmental monitoring within an educational context. Expect a useful range roughly between 0°C and 50°C, with an accuracy of around ±1°C to ±2°C. It’s not intended for scientific-grade precision or extreme temperatures.
• Response Time: Like most integrated sensors, it doesn’t react instantly to rapid ambient temperature changes. There’s a lag as the chip itself heats or cools. Patience is needed for accurate ambient readings.
• Internal Heat Source: Never forget that the processor generates heat. Performance-intensive tasks like complex animations or heavy radio use will significantly raise the reported microbit temperature sensor reading.
• Placement: Where you position the micro:bit matters. Avoid covering it with insulating materials (like fabric or thick tape) if you want